The present invention is directed to improvements in passive impedance matching devices for coupling signals from a source, such as a host computer, to a plurality of utilization devices, such as other computers, terminals or peripheral devices. More particularly, the invention relates to a device in which a host computer controls a network or system of a plurality of remote computers or terminals (e.g., the host initiates and the terminals do not talk to each other.)
Computer networking is a very useful system for allowing a host computer to communicate with a plurality of terminals. Active and passive coupling systems and devices are widely used in the art; the present invention is a passive coupling device. Most commercial passive coupling devices do not properly impedance match over wide frequency ranges and those that do are complex and relatively expensive.
The object of the present invention is to provide an improved passive impedance matching device which is economical and effective over a wide frequency range.
A passive impedance matching device according to the invention incorporates a power splitter comprised of a center tapped bifilar wound coil on a core and shunted by a resistance or impedance having a predetermined value. A pair of these power splitters have their center taps connected to commonly receive input signals from a host computer, for example. This arrangement creates a virtual ground and thus avoids the need to create an unbalanced (single sided) signal. By cascading stages, the input signal can be split and impedance matched may times and be operative over a wide frequency range. Where only a particular number of outputs, less than the number of outputs available by cascading, are used, the unused outputs are terminated with their characteristic impedance.